Clackmae Bridge, near Earlston, is to be closed for 10 weeks to allow major refurbishment and strengthening works to be carried out.
The single-arch bridge, on the C76 back road between Earlston and Lauder, will be shut from Monday, October 16, to Friday, December 22.
Its deck is to be replaced during that time, as well as strengthening works being carried out.
Diversions will be in place, with the signed alternative route being via the A68 through Earlston, the D4/4 at South Blainslie and the C76.
The £690,000 works are part of a £2m programme of bridge repairs also including improvements to Lowood Bridge, between Galashiels and Melrose; Bowanhill Bridge, near Teviothead; and Bowden Church Bridge, west of Newtown.
Scottish Borders Council’s executive member for roads and infrastructure, Selkirkshire councillor Gordon Edgar, said: “The C76 road is an important route for the local community, which is why the council is carrying out these works to Clackmae Bridge.
“It is part of a significant bridge repairs programme by the council in 2017-18 which will ensure Clackmae Bridge, alongside a number of other important bridges in the Borders, can continue to be used for years to come.”
Clackmae Bridge is one of more than 1,100 crossings region-wide that the council is responsible for maintaining.